flutter - 在空 flutter 上调用getter 'text'

Question

我的Flutter应用程式中出现这个错误:

NoSuchMethodError: The getter 'text' was called on null. Receiver: null Tried calling: text See also: https://flutter.dev/docs/testing/errors

import 'package:flutter/material.dart';

void main() {
  runApp(
    NewApp()
  );
}

class NewApp extends StatefulWidget {
  NewApp({Key key}) : super(key: key);

  @override
  _NewAppState createState() => _NewAppState();
}

class _NewAppState extends State<NewApp> {
  TextEditingController textController;

  @override
  Widget build(BuildContext context) {
    return Container(
       child: Column(
         children: <Widget>[
           TextField(
            controller: textController,
          ),
          Text(
            textController.text
          )
         ],
       )
    );
  }
}

Answer 1

看来您尚未初始化TextEditingController。您可以在这样声明时进行初始化，

TextEditingController textController = TextEditingController();

在使用它之前，必须对其进行初始化，否则实例textController保持为空，而textController.text在null上被调用。